1. Field of the Invention
The present invention relates to reproduction apparatuses and reproduction methods, and more particularly, to a reproduction apparatus and a reproduction method for a recording medium of a reproduction type in which data is reproduced by irradiating with laser light and applying a magnetic field.
2. Description of the Related Art
As a recording medium that allows data to be rewritten (overwritten), magneto-optical disks are known.
There are known, for example, a light-intensity-modulation overwrite method and a magnetic-modulation overwrite method to perform recording in the magneto-optical disks.
In the light-intensity-modulation overwrite method, an external magnetic field having a constant bias is applied to a magneto-optical recording film (signal recording surface) of a magneto-optical disk, and the n the film is irradiated with laser pulses having a required power and modulated by recording data. With these operations, a part of th e magneto-optical recording film irradiated with the laser pulses and heated has the magnetization direction corresponding to the external magnetic field, and hence a recording pit is formed.
There have been proposed several types of magnetic-modulation overwrite methods. Basically, the magneto-optical recording film is irradiated with laser light having a recording level, and then an external magnetic field modulated by recording data is applied. With these methods, a area having the magnetization direction corresponding to the polarity of the external magnetic field is formed, and hence, a recording pit is formed.
To reproduce data from a magneto-optical disk in which the data has been recorded in one of the foregoing ways, the magneto-optical recording film, which serves as a signal recording surface, is irradiated with laser light by an optical pickup. The laser light reflected from the magneto-optical recording film rotates its polarizing plane by a so-called magnetic Kerr effect. The optical pickup reads a recording pit, namely, reproduces the data with the use of light-amount differences of the reflected light, obtained from the magnetic Kerr effect.
Therefore, when a magneto-optical disk is used, a magnetic field is required to be applied during recording in any of the above methods, but a magnetic field is not necessarily required to be applied during reproduction.
The applicant of the present application has already proposed a magnetically induced super resolution (MSR) method to enable higher-density recording in an magneto-optical disk.
In this MSR method, to describe it simply, information recorded in an area smaller than a laser spot diameter is read by the use of a plurality of magnetic-film layers having different temperature characteristics.
To reproduce data from a disk by the MSR method, it is necessary to constantly apply an external magnetic field having a required constant bias to the magnetic film of the disk. Therefore, a disk drive apparatus that allows data to be reproduced from a magneto-optical disk by the MSR method needs to be provided with a structure for generating the external magnetic field. The structure may include, for example, a magnet and a driving circuit for driving the magnet to generate a magnetic field.
To generate a magnetic field from the magnet, it is necessary, for example, to output a driving current from the driving circuit to the magnet. Conversely, as described above, since an external magnetic field is unnecessary during reproduction for a magneto-optical disk not employing the MSR method, it is unnecessary to cause a driving current to flow into the magnet.
Consequently, in terms of power consumption during reproduction, the MSR method is inferior because it requires the driving current.
Accordingly, it is an object of the present invention to reduce power consumption required for generating an external magnetic field as much as possible even in a reproduction method that needs the external magnetic field to be applied during reproduction.
The foregoing object is achieved in one aspect of the present invention through the provision of a reproduction apparatus for reproducing a signal recorded by magnetizing a recording layer, from a recording medium by transferring the direction of the magnetization to a reproduction layer, including an optical pickup for emitting laser light to a predetermined position on the recording medium; a magnetic-field generation means disposed correspondingly to the optical pickup, for applying a biased magnetic field to the recording medium for signal reproduction; and control means for performing at least a reproduction operation in which the optical pickup is moved above the recording medium and a signal is read from the recording medium, and a still operation in which the optical pickup is held at a predetermined position above the recording medium and a signal is not read from the recording medium, wherein the control means drives the magnetic-field generation means during the reproduction operation to apply a biased magnetic field to a position on the recording medium where laser light is irradiated, and stops driving the magnetic-field generation means during the still operation so as not to apply a biased magnetic field to the recording medium.
The foregoing object is achieved in another aspect of the present invention through the provision of a reproduction method for reproducing a signal recorded by magnetizing a recording layer, from a recording medium by transferring the direction of the magnetization to a reproduction layer, including the steps of determining the type of the recording medium by emitting laser light to a predetermined position on the recording medium; applying a biased magnetic field for signal reproduction to a position where the laser light is irradiated, according to the determination result; and controlling such that at least a reproduction operation for reading a signal from the recording medium and a still operation in which an optical pickup is held at a predetermined position above the recording medium and a signal is not read from the recording medium are performed, and a biased magnetic field is not applied to the recording medium during the still operation.
With the above structure, a magnetic field is not applied to a recording medium in a period when an operation is not executed to read data from the recording medium. In other words, a driving power for applying the magnetic field is unnecessary during this period.